Electrode construction



May 30, 1933. A. L. BRANDT, SR

ELECTRODE CONSTRUCTION Filed Sept. 2, 1931 INVENTR l WL ,Si BY Ma( j ATTORNEYS Patented May 30, 1933 UNITED STATES PATENToFI-ICE ALFRED L. BRANDT, SR., OF BUFFALO, NEW YORK, ASSIGNOR T FLEXLUME CORPORA- TION, OF TONAWANDA, NEW YORK, A CORPORATION 0F NEW YORK ELECTRODE CONSTRUCTION `Application led September 2, 1931. Serial No. 560,693.

rIhis invention relates to electroluminescent tubes which employ an inert gas such as neon as a luminescent medium4 and more particularly to improvements in electrode con- 5 structions therefor of the type disclosed in the co-pending application of Edward S.

Woolrich, Serial No. 368,7 89.

An electrode construction of this type includes an electrically conductive element having an active surface exposed to the interior of the tube and means associated with said element but insulated therefrom for controlling the stream of ions in the vicinity of the element so as to prevent heating of the active surface thereof to such a degree as to cause vaporization of the electrode metal.

The means by which the stream of ions is controlled absorbs a considerable part of the heat generating energy of the stream and hence reduces to a considerable extent the heating action of the stream upon the element. This not only enables the use of electrode elements having relatively small active surfaces but also insures a low voltage drop across the elements.

One object of the present invention is to provide a novel construction and arrangement of the means by which the stream of ions is controlled.

A further object is to provide an electrode construction which is economical to manufacture and which is capable of withsfanding rough treatment incident to its transportation, installation and operation.

The invention is illustrated in the accompanying drawing, in which:

Figure 1 is a longitudinal section taken through the center of a terminal portion Aof a tube which carries an electrode constructed in accordance with the invention. i A

Figure 2 is a section taken along line 2 2 ofiFigure 1.

Figure 3 is a of Figure 1.

section taken along line 3 3 Figure 4 is a section taken along line 4--4 of Figure l. The electroluminescent tube is sufficiently indicated by showing its terminal portion 5 in which the reentrant stem 6 is provided with a seal 7 through which the lead-in wire 8 passes. The electrode element 9 to which the leadfin wire is connected may be composed of any suitable material and fashioned in any suitable form.v Preferably it is of a high magnesium content and is formed with a cylindrical chamber 9a, the Walls of which provide an active surface exposed to the interior of the tubethrough the open end of the element. The connection between the -lead-in Wire 8 and the electrode element may be conveniently effected by embedding the end ofthe said Wire in the wall lO which closes the outer end of the element.

The electrode element 9 is axially located with respect to the tube within a cylindrical chamber provided by an insulating sleeve 11. The latter conforms roughly to and fits somewhat closely over the element 9 and in a like electrode carrying and body portions of the tube to prevent axial movement of the sleeve in the direction of the body of the tube. AX- ial movement of the sleeve in the opposite direction is prevented by the lead-in wire 8 or if desired the end of the sleeve 11 may be eX- tended to abut the end of the electrode carryino' portion of the tube.

The electrode element is held within the 50 end of the electrode adjacent the shell 13 is sleeve 11 against axial displacement in the direction of the seal 7 by an indentation 1Q formed in the sleeve and against axial displacement in the opposite direction by the lead-in Wire 8.

The means by which the stream of ions is controlled may have various forms, but is preferably in the form of a tapered or conical shell 13 of foraminous construction. In accordance with the invention of the shell 13 which is located axially of the tube is carried Within the flared portion 11a of the sleeve 11. The shell is preferably tapered to the same degree as the flared portion of the sleeve and the former, therefore, ts conformably within the latter. The shell is held against axial movement in the direction of the electrode element 9 by the taper of the sleeve and it may be held against axial movement in the opposite direction by heating the outer end of the sleeve and Working it slightly over theY enlarged end of the shell as at 14, that is, Where the sleeve is of glass.

As described in the application of Edward S. Woolrich to which reference has been made, the shell 13 provides an equipotential surface, that is to say a surface any point of which tends to repel the current in a direction normal tolthe said surface. Hence the stream of ions is concentrated by the shell 13 toward the axis of the tube adjacent the open end of the electrode element 9. The concentration of the ions is increased by the tapered form of shell shown, the latter being arranged Within the sleeve 11 with such relation to the element 9 as to direct the concenj trated stream of ions into the'chainber 9a before it is dispersed by the action of the said element. Thus, the dispersion of the ions takes place Within the chamber 9a whereby anyof the electrode metal which may be vaporized will be deposited upon the Walls of the chamber, this action tending to perpetuate the life of the electrode and also prevent dissipation of the gaseous conducting medium Within the tube. It will be apparent, therefore, that in concentrating the stream of ions in the vicinity of the electrode element, and causlng it to enter the chamber 9a thereof before dispersion, has the advantage that the protected from the bombarding action of the current, thereby preventing portions thereof from spattering upon the Walls of the sleeve 11 adjacent the open end of the electrode element..

In concentrating the stream of ions in the manner descrlbed, the shell 13 absorbs a considerable part of the heat generatingenergy l 'o f the stream thereby reducing to a substantial extent the heat generating characteristics of that portion of the stream-of ions Within the chamber 9a f the electrode element. This had the advantage of maintaining the electrode element at a relatively low temperature during normal operating conditions and as a result thereof it is possible to employ electrodes having relatively small acti-ve surfaces Without possibility, because of overheating, of disintegration or vaporization of the electrode metal to such an extent as to impair the life of the tube.

In the manufacture of electroluminescent tubes it is necessary to remove from the electrodes and the Walls of the tube impurities usually present in the forln of a gas in order to prevent contamination of the gaseous conducting medium during the operation of the tube. To this end, it is the practice to purify the electrodes and the tube Walls by passing a current through the tube of a voltage and amperage high enough to heat the said electrodes and tube Walls to a temperature high enough to drive off such gases. During this operation, which is termed .bombarding the gaseous impurities are driven off by the heating action of the current and are Withdrawn from the tube by evacuating the latter. It will be apparent, therefore, that the use of small electrodes Will enable the clearing up of the tube during the bombarding operation in Va short time with a correspondingly small current consumption.

In bombarding lthe tube it' is desirable to observe the action of the current Within the chamber 9a of the electrode element in order to ascertain Whether the entire surface of the chamber is being alfected by the bombarding action. To this end the...electrode element is preferably formed with openings 15 adjacent the bottom Wall 10 thereof. y

In the bombarding operation it is also, necessary that the shell 13 be heated to such a degree as to insure removal of any impure gases which may be present in it. In order to facilitate the heating of the shell 13, therefore, a member 16 Which is shown in the form' l manufacturing standpoint and is capable of withstanding rough treatment incident to transporting and installing operations.`

I claim as my invention:

1. An electrode construction for electro-' luminescent tubes comprising in combination Withfsuch a tube, an electrode, a hollow body Within which said electrode is carried, means for supporting said body in said tube in spaced relation to the walls thereof and electrically conductive means carried by said body and insulated from said electrode for controlling the stream of ions in the vicinity of the electrode to prevent volatilization of the latter.

2. An electrode construction for electro- .sleeve and insulated from said electrode for controlling the stream of ions in the vicinity of the electrode to prevent volatilization of the latter. 1

3. An electrode construction for electroluminescent tubes'comprising in combination with such a tube, an electrode, a sleeve vwithin which said electrode is carried, means for supporting said sleeve Within said tube in spaced relation to the walls thereof and electrically conductive means carried Within said sleeve and insulated from said electrode for controlling the stream of ions inthe vicinity of the electrode to prevent volatilization of the latter.

L An electrode construction for electro! luminescent tubes having re-entrant stems comprising in combination with such a tube, an electrode, a sleeve within which said electrode is carried, said sleeve fitting over a reentrant stem of said tube and electrically conductive means carried by said sleeve and insulated from said electrode for controlling the stream of ions in the vicinity of the electrode to prevent volatilization of the lat-I ter. A

5. An electrode construction for electrolumineseent tubes having re-entrant stems comprising in combination with such a tube an electrode, a sleeve Within. which said electrode is carried, said sleeve fitting over a reentrant stem of said tube and electrically conductive means carried within said sleeve and insulated from said-electrode for controlling the stream of ions in the vicinity of the electrode to prevent volatilization of the latter.

6. An electrode construction for electroluminescent tubes having r'e-entrant stems comprising in combination with such a tube, an electrode, an insulating sleeve Within which said electrode is carried, said sleeve fitting over la re-entrant stem of said tube and electrically conductive means carried b prevent volatilizacarried by said sleeve and insulated from said thereby causing the said stream electrode for concentrating the stream of ions in the vicinity of the electrode and thereby causing the said stream to enter the open end of the electrode.

18. An electrode construction for electroluminescent \tubes comprising in combination with such a tube, a hollow electrode open at one end, a sleeve within which said electrode is carried, said sleeve Haring out Wardly at a point beyond the open end of said electrode and an electrically conductive element fitting Within the flared portion of said sleeve and insulated from said electrode, said element concentrating the stream of ions in the vicinit of the electrode and to enter the open end of the electrode.

9. An electrode construction for electroluminescent tubes comprising in combination with such a tube, a hollow electrode open `at one end, a sleeve within which said electrode is carried, said sleeve fiaring outwardly at a point beyond the open end ofsaid electrode and an electrically conductive element t' ting Within the flared portion of said sleeve and insulated from said electrode, said element having a relatively large open end in the direction of the body ofthe tube and tapering in the direction of the electrode to a relatively smaller opening, whereby the stream of ions in the vicinity of the electrode is concentrated and thereby caused to enter the open end of the electrode.

l0. An electrode construction for electroi ,luminescent tubes comprising in combination vicinity of the electrode and causing the said stream to enter the open end of the electrode.

11. An electrode construction for electroluminescent tubes comprising in combinatlon 'with such a tube, a hollow electrode open at one end, a sleeve within which said electrode is carried, said sleeve flaring outwardly at a point beyond the open end of said electrode and a foraminous electrically conductive eley ment fitting Within the flared portion of said said sleeve and insulated from said electrode for controlling the stream of ions in the sleeve and insulated from said electrode, said element having a relatively large open end in the direction of the body of the tube and tapering in the direction 0f the electrode to a relatively smaller opening, 1 whereby the stream of ions in the vicinity of the electrode is concentrated and caused to enter the open end ofthe electrode.

12. An electrode construction for electroluminescent tubes comprising in combination with such a tube, an electrode, a. sleeve Within' which said electrode is carried, means for supporting'said sleevewithin said tube in spaced relation to the walls thereof, an elec- 5 trically conductive shell insulated from said electrode for controlling the stream of ions in the Vicinity of the electrode and supplemental means for heating saidy shell t0 eX- pedite the removal of the impurities present in said shell and Whose continued presence would result in contamination of the gaseous Y conductive medium with which the tube is to be .filled In testimony whereof I hereby aflix my signature v ALFRED L. BRANDT, SR. 

